Fluorinated hydrocarbons have many uses, one of which is as a cleaning agent or solvent to clean, for example, electronic circuit boards. Electronic components are soldered to circuit boards by coating the entire circuit side of the board with flux and thereafter passing the flux-coated board over preheaters and through molten solder. The flux cleans the conductive metal parts and promotes solder fusion, but leave residues on the circuit boards that must be removed with a cleaning agent.
Preferably, cleaning agents should have a low boiling point, nonflammability, low toxicity, and high solvency power so that flux and flux-residues can be removed without damaging the substrate being cleaned. Further, it is desirable that cleaning agents that include a fluorinated hydrocarbon be azeotropic or azeotrope-like so that they do not tend to fractionate upon boiling or evaporation. If the cleaning agent were not azeotropic or azeotrope-like, the more volatile components of the cleaning agent would preferentially evaporate, and the cleaning agent could become flammable or could have less-desirable solvency properties, such as lower rosin flux solvency and lower inertness toward the electrical components being cleaned. The azeotropic property is also desirable in vapor degreasing operations because the cleaning agent is generally redistilled and reused for final rinse cleaning.
Fluorinated hydrocarbons may also be used as refrigerants. In refrigeration applications, a refrigerant is often lost during operation through leaks in shaft seals, hose connections, solder joints, and broken lines. In addition, the refrigerant may be released to the atmosphere during maintenance procedures on refrigeration equipment. Accordingly, it is desirable to use a single fluorinated hydrocarbon or an azeotropic or azeotrope-like composition that includes one or more fluorinated hydrocarbons as a refrigerant. Some nonazeotropic compositions that include one or more fluorinated hydrocarbons may also be used as refrigerants, but they have the disadvantage of changing composition, or fractionating, when a portion of the refrigerant charge is leaked or discharged to the atmosphere. If a non-azeotropic composition contains a flammable component, the blend could become flammable because of such a change in composition. Refrigerant equipment operation could also be adversely affected due to the change in composition and vapor pressure that results from fractionation.
Azeotropic or azeotrope-like compositions of fluorinated hydrocarbons are also useful as blowing agents in the manufacture of close-cell polyurethane, phenolic and thermoplastic foams. Insulating foams require blowing agents not only to foam the polymer, but more importantly to utilize the low vapor thermal conductivity of the blowing agents, which is an important characteristic for insulation value.
Aerosol products employ both single component fluorinated hydrocarbons and azeotropic or azeotrope-like compositions of fluorinated hydrocarbons as propellant vapor pressure attenuators in aerosol systems. Azeotropic or azeotrope-like compositions, with their substantially constant compositions and vapor pressures, are useful as solvents and propellants in aerosols.
Azeotropic or azeotrope-like compositions that include fluorinated hydrocarbons are also useful as heat transfer media, gaseous dielectrics, fire extinguishing agents, power cycle working fluids such as for heat pumps, inert media for polymerization reactions, fluids for removing particulates from metal surfaces, and as carrier fluids that may be used, for example, to place a fine film of lubricant on metal parts.
Azeotropic or azeotrope-like compositions that include fluorinated hydrocarbons are further useful as buffing abrasive detergents to remove buffing abrasive compounds from polished surfaces such as metal, as displacement drying agents for removing water such as from jewelry or metal parts, as resist-developers in conventional circuit manufacturing techniques employing chlorine-type developing agents, and as strippers for photoresists when used with, for example, a chlorohydrocarbon such as 1,1,1-trichloroethane or trichloroethylene.
Some of the fluorinated hydrocarbons that are currently used in these applications have been theoretically linked to depletion of the earth's ozone layer and to global warming. What is needed, therefore, are substitutes for fluorinated hydrocarbons that have low ozone depletion potentials and low global warming potentials.